The present invention relates to a pneumatic tire, more particularly to an improvement in a lower sidewall portion being capable of preventing the occurrence of bareness of rubber on the tire outer face.
When a green tire is put in a vulcanizing mold and inflated to press the outer face of the tire against the inner face of the mold, the contact between the two faces is liable to delay near the radially outer end of a bead apex because the bead portion is relatively stiff. In such a portion, therefore, air between the tire and mold is liable to remain and as a result, bareness of rubber is liable to occur on the outer face of the finished tire.
In order to cause escape of air between a tire and mold, conventionally vent hole are provided at corresponding portions of the mold. However, the portions in which vent holes are necessary vary depending on tire components such as a hard rubber bead apex, carcass ply turnup, reinforcing cord layer and the like. Therefore, if positional unevenness of the end or edge of such tire component is large, air cannot be fully removed. Further, a more important point is that the mold cost is very high. If the internal structure of the tire is changed for some reason and the position of the end or edge of a tire component is accordingly changed, it is necessary to remake the mold.
In Japanese patent No. 2872920, a radial tire is disclosed wherein as shown in FIG. 6, the convexly curved outer face of the tire sidewall portion SW is provided with a circumferentially extending groove G to prevent bareness of rubber. This groove G has a width of from 2 to 10 mm and a depth of from 0.5 to 1.5 mm, and the position of the groove G is such that the distance (A) measured radially inwardly from the radially outer end P of a bead apex Bap to the radially outer edge Ga of the groove G is in a range of from 0 to 7 mm. Although this groove G is effective, in order to prevent bareness of rubber without fail, an increase in the size especially depth Gc of the groove is unavoidable. As a result, the appearance and strength of the tire are liable to become worse.
It is therefore, an object of the present invention to provide a pneumatic tire in which the occurrence of bareness of rubber near the radially outer end of a bead apex is effectively prevented without affecting the appearance and strength of the tire, and further the occurrence can be prevented even if the position of the end or edge of a tire component is changed intentionally or not.
According to the present invention, a pneumatic tire comprises
a tread portion,
a pair of sidewall portions,
a pair of bead portions with a bead core and a bead apex therein,
each of the sidewall portions provided on the outer face with means of escaping air between the tire and a mold for vulcanizing the tire, which means comprises
a circumferentially extending vent emboss line disposed adjacently to a radially outer end of the bead apex and
a circumferentially extending vent groove adjoining the radially outside of the vent emboss line and having a depth of at least 0.15 mm.
Preferably, the vent emboss line and vent groove are disposed in a lower sidewall region having a substantially straight profile in a tire meridian section which region extends radially inwardly from a position radially inside the maximum tire section width point towards the bead portion. And, the bottom of the vent groove is substantially parallel to this straight profile of the lower sidewall region and is provided with emboss marks.